Selling on Amazon comes with a steep learning curve, especially when it comes to supply chain logistics. Vendors need to navigate a maze of terms, processes, and compliance requirements to keep products moving efficiently on Amazon Vendor Central.
In this guide, we break down key supply chain terms, explain the difference between collect and prepaid freight, and highlight the importance of advanced shipment notifications (ASNs) to help Amazon vendors stay in control and avoid costly mistakes.
Understanding key Amazon supply chain terms
To succeed as an Amazon vendor, you need to understand the key supply chain terms used throughout Vendor Central and the fulfilment network.
ASIN (Amazon Standard Identification Number)
An ASIN is Amazon’s unique identifier for each product. It ensures the right product appears in the marketplace and prevents listing errors. Getting the ASIN right is essential for visibility and accuracy in Amazon Product Listings.
Carton vs. Master Pack vs. Unit
Amazon structures its packaging to keep warehouse operations smooth and efficient:
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Unit – The smallest sellable item with a barcode, such as an individual bottle or box.
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Carton (case pack or inner pack) – A box containing multiple units.
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Master pack – The largest shipping container, holding multiple cartons for bulk transportation.
Make sure you input items per inner pack (IPIP) and inner packs per master pack (IPMP) correctly. These values impact purchase order (PO) quantities, how Amazon receives stock, and how it appears on detail pages.
ARN (Amazon reference number)
The Amazon reference number (ARN) is generated when a routing request is submitted for collect shipments. Amazon uses it to track and process deliveries.
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Collect vs. Prepaid Freight: Which Model is Right for You?
Amazon offers two freight payment models for vendors – collect (WePay) and prepaid (TheyPay). Choosing the right one impacts costs, responsibility, and control over shipments.
Collect Freight (WePay)
With collect freight, Amazon pays for transportation and selects the carrier. Vendors don’t need to manage logistics beyond having products ready for pickup. However, Amazon controls pickup times, carriers, and routing.
Prepaid Freight (TheyPay)
With prepaid freight, the vendor covers all transport costs and manages the shipment. This provides more flexibility over delivery schedules and carrier selection, but vendors must comply with Amazon’s freight ready date (FRD) and schedule through Carrier Central.
Which One Should You Choose?
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If cost control is a priority → Collect freight shifts transportation costs to Amazon.
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If you need flexibility and control → Prepaid freight gives you more control over shipments.
Why Advanced Shipment Notifications (ASNs) Matter
An advanced shipment notification (ASN) is an electronic packing list vendors send before their shipment arrives at an Amazon fulfilment centre (FC). It ensures faster processing and fewer errors, helping with chargeback recovery and reducing penalties.
The Benefits of ASNs
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Faster processing – Amazon matches shipment details against purchase orders before arrival.
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Reduced errors – Identifies mismatches between shipped goods and expected inventory early.
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Improved compliance – Prevents chargebacks and delays from missing or incorrect shipment data.
How to Ensure ASN Compliance
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Submit ASNs for all shipment types – truckload (TL), less-than-truckload (LTL), and small parcel (SP).
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Ensure carton labels match ASN details (serial shipping container code, AMZNCC, or GTIN-14).
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Double-check for missing or incorrect product IDs before dispatching to prevent rejected shipments.
Common Pitfalls and How to Avoid Them
Even experienced vendors run into supply chain issues on Amazon. Here are some of the most common mistakes and how to avoid them.
Incorrect Carton and Master Pack Configuration
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Issue: Vendors miscalculate the number of units per carton or master pack, leading to incorrect purchase orders.
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Fix: Verify IPIP and IPMP settings in Amazon Vendor Central before confirming a listing.
Missed Freight Appointments
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Issue: Late or missed deliveries due to unavailable Carrier Central slots.
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Fix: Book slots early and confirm delivery windows with carriers.
ASN Mismatches
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Issue: Discrepancies between the ASN and received shipments cause delays and chargebacks.
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Fix: Review ASN details against the actual shipment before dispatching.
Pricing & Invoice Mismatches
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Issue: Invoiced product costs don’t match the purchase order, triggering disputes.
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Fix: Ensure product IDs and agreed costs align with purchase orders.
Final thoughts
Mastering Amazon’s supply chain isn’t just about meeting compliance – it’s about running a seamless, efficient operation that drives profitability. Understanding ASINs, freight models, and ASNs helps vendors avoid penalties, reduce delays, and stay competitive.
For vendors who want to stay in control, precision is key. Get your packaging, shipping, and invoicing right, and Amazon’s supply chain can fuel your growth instead of holding you back.
Meta description: Learn how to optimise your Amazon supply chain, avoid costly mistakes, and streamline Vendor Central operations with this expert guide from WAKE.
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